1. Field of the Invention
The present invention relates to a thermosensitive recording medium which can be suitably used for one-time-only image recording and for repeated image recording and image erasure; an image recording method; and an image processing method.
2. Description of the Related Art
In the case where laser light is used for recording onto a thermosensitive recording medium, there is a technique of providing a light-heat conversion layer made of a metal film formed by vacuum vapor deposition of titanium, chromium, nickel, germanium, aluminum or the like (refer to Japanese Patent Application Laid-Open (JP-A) No. 05-8537). However, the light-heat conversion layer made of the metal film is problematic in that it has metallic luster and is therefore inferior in visibility, it peels off as time passes, etc.
To obtain a thermosensitive recording medium free of such problems, there is a technique of using an organic pigment, e.g., phthalocyanine, as a light-heat conversion material (refer to JP-A Nos. 11-−151856, 2004-345273, 2005-238745 and 2005-238746). In this case, however, the organic pigment generally has low resistance to light and is problematic in that, especially when mixed with a leuco dye, the organic pigment decomposes with time owing to the interaction between the organic pigment and the leuco dye, thereby causing a decrease in absorption in the near-infrared region and thus a noticeable decrease in recording sensitivity and erasure sensitivity.
Nowadays, use of thermosensitive recording media as thermoreversible recording media in product delivery and distribution centers, etc. is becoming more and more popular (refer to JP-A Nos. 2000-136022 and 2004-265247 and Japanese Patent (JP-B) No. 3998193).
However, use of a thermoreversible recording medium including an organic pigment, e.g., phthalocyanine, as a light-heat conversion material has caused new problems in which the background discolors with time and additional writing is difficult after the thermoreversible recording medium has been left unattended in an outdoor environment, etc.
Hence, in reality, there is a demand for provision of a thermosensitive recording medium which exhibits superior technical effects; and an image recording method and an image processing method which use the thermosensitive recording medium. The superior technical effects include securing favorable visibility without metallic luster, coloration, etc., securing favorable recording sensitivity and erasure sensitivity without their temporal decrease, preventing temporal discoloration of the background, removing the difficulty in performing additional writing after the thermosensitive recording medium has been left unattended in an outdoor environment, etc., and preventing degradations, such as peeling off of a film, deformation and elongation, caused by repeated use of the thermosensitive recording medium.